It is well known that coatings used on metals and nonmetals often contain various hazardous and toxic substances. When these coatings are removed or begin to fall off, the offending hazardous and toxic substances can create a risk to the environment and to humans exposed through work and living environments. This is especially the case in the abrasive, mechanical and chemical removal of paint coatings such as the sand blasting of lead-based painted steel structures, the use of power tools on all types of surfaces or the use of chemical strippers. Additionally, abrasive or mechanical removal systems create a considerable amount of dust along with the paint waste generated. Both the dust and the wastes can contain the hazardous and toxic substances. Workers and the environment must be shielded from the waste and the dust through expensive containment systems and hazardous waste disposal procedures. The U.S. Environmental Protection Agency has included many of the ingredients of coatings, such as heavy metals, as hazardous substances which then become regulated waste material when removed. These wastes include heavy metals such as chromium, silver, lead, arsenic, barium, cadmium, selenium, mercury, zinc and others as well as polyvinyl chlorides, PCB, 2BHC and like toxins.
In many of the known removal processes, the hazardous substances create troublesome disposal and handling problems. Consequently, various types of systems have been devised to reduce, minimize or eliminate the hazard posed by coatings both in place and as wastes when removed. For example, vacuum recyclable abrasive blasting systems provide a closed loop in which a positive pressure and a variable recycling system provide good removal. Typically, steel or iron, grit or shot are used as the operative abrasive. A negative pressure or vacuum is applied to a hose positioned against the surface on which the coating to be removed is located and which collects the spent abrasive and removed coating with minimal exposure to the atmosphere. The collected wastes and reusable abrasives are separated through known separation techniques.
Nonvacuum removal techniques require the containment and collection of the spent abrasive and paint waste to prevent environmental exposure. Containment, dust control and waste minimization activities are time consuming and expensive. In both methods, disposal of the waste is a significant problem.
In some cases, it is determined that managing a coating in place is more cost effective in the short term. In such cases, an encapsulant or over-coating is used to immobilize a peeling or chipping surface. The encapsulant acts to overcoat and bind any chipping or peeling paint to the substrate and prevent any of the toxic or hazardous elements from entering the environment. The encapsulant process does not remove or abate the deteriorating coating. Rather, it manages the problem in place to be dealt with at a later time. The hazardous or toxic elements are still present and will represent a disposal problem at a later time.
Many times architectural components are removed in their entirety. The components (such as door frames, windows, moldings, etc.) when tested in accordance with EPA procedures, and if painted with lead based paint, often result in the components being a hazardous waste. The treatment of this waste is so complicated and expensive that the EPA is considering granting an exemption from the hazardous waste regulations. This would allow great quantities of materials to be placed in non-hazardous waste landfills completely untreated. This present invention provides an economical method for rendering such wastes non-hazardous.
One method of treating solid hazardous waste containing unacceptable levels of leachable metals is set forth in U.S. Pat. No. 5,037,479 in which the solid waste is mixed with a buffering agent such as magnesium oxide or hydroxide and a salt or acid such as triple superphosphate, ammonium phosphate or diammonium phosphate. The method provides a way of converting hazardous wastes to a substantially nonleachable form. See also U.S. Pat. No. 4,889,640 for a similar method of treating hazardous wastes and Methods to Treat EP Toxic Foundry Wastes and Waste waters, AFS Transactions, 1985, p. 737–740. See also U.S. Pat. Nos. 5,266,122 and 5,439,527.
Accordingly, it is an object of the present invention to provide compositions and methods for their application to remove coatings that include a hazardous substance and prevent the removed waste from becoming a hazardous byproduct. It is a further objective of the invention to provide a method that facilitates compliance with the requirements of the various agencies regulating environmental exposure to hazardous substances. It is a further objective to provide a removal method and compositions for use therein which facilitates the handling and disposal of any waste in a manner which renders it exempt from regulation and which is both cost effective and practical to use.